1. Field of the Invention
This invention relates to miniature switches for use in electrical circuits, and more particularly pertains to miniature push button electrical switches employing a ratchet mechanism.
2. Description of the Related Art
A number of different types of push button actuated switch mechanisms have been developed to fulfill the function of making and breaking electrical contact upon depression of a button. Of particular interest, for the purposes of the present invention, are those mechanisms that employ a ratchet mechanism that serves to convert depression of a button to incremented rotation of a first electrical contact within the switch. The switch is configured such that this incremented rotation of the first electrical contact causes it to alternately engage and disengage a stationary second electrical contact within the switch. An electrical connection is thereby alternately made or broken upon each depression of the button.
A disadvantage or shortcoming typically inherent in such ratchet mechanism type push button switches is the fact that electrical continuity between the two contacts is broken immediately upon initial depression of the push button, or more correctly, upon initial displacement of the activating plunger. Conversely, should the movement of the plunger be impeded so as to prevent complete extension thereof, the contacts can not make contact with one another, and consequently, the switch effectively fails to function. The free extension of the plunger may be impeded by, for example, physical contact with its surroundings due to its orientation in a particular installation or due to binding of the entire mechanism caused by distortion of the as a result of too tight a fit within a mounting surface.
This described shortcoming poses a particularly bothersome nuisance on a high-speed assembly line of automobiles where the time required to carefully and properly install each of perhaps a multitude of such switches may simply not be available. A misaligned installation or perhaps the overtightening of a fastner can result in an obstruction of the plunger's movements, and as was alluded to above, will prevent the switch from closing a circuit. The entire circuit will therefore appear not to function requiring a diagnosis of the problem to be undertaken and after isolation of the fault, the switch would ultimately have to be replaced or appropriate adjustments in the reinstallation made. Hurried assembly, apathetic workmanship, or tolerance stack-up can contribute to the misinstallation of such switches, subsequently requiring these extra remedial measures. It has long been recognized that a ratchet mechanism push button switch design is needed that is not sensitive to minor interference with movement of the plunger in order to increase the efficiency of high volume assembly lines and provide trouble-free service.